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Full text of "Text Book Of Mechanical Engineering"

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Appendix VI.

anvil because the ports at j are all closed, and the air cushion
under piston B prevents the blow. Moving K downwards, the
air underneath B is wholly or partially released, and the tup
therefore strikes the anvil with whatever force may be desired,
while a rapid opening and closing of K will effect a single blow.
The valve T automatically opens to admit air on the upstroke,
and the upper part of cylinder H is always open to the
atmosphere.

Pig. 928 is a diagram of velocities, where the ordinates vc
indicate the uniform velocity of the crank pin of 5*88 ft. per sec.,
and the radial ordinates v^ within the curve shew the velocity of
the lever pin for any given position in the vibration. It will be
seen that the latter becomes 9*5 ft. per sec. on the downstroke,
or much greater than the velocity of the crank pin, and proves
the smartness of the blow as conferred by the mechanism.

JP. 100. The Drop Hammer, Fig. 929, is now much used
for stamping purposes, and the blow is caused entirely by the
"action of gravity on the tup. The bed T carries two side
standards B B, and the anvil N ; and the tup c is free to fall

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